The invention concerns an apparatus for ultrasonically vibrating depleted uranium alloy rods to reduce residual stress and the quench sensitivity of the rods.
In the processing of depleted uranium alloy rods (DU), the rods are heated into the gamma phase region and then water-quenched from 850.degree. C. to bring about the martensitic structure. The material is extremely quench sensitive so that the quenching is undertaken at a precisely controlled rate. A fast quench may cause center voids because of the large differences in the thermal contraction valves of the phases present. A slow quench does not achieve the desired martensitic structure. Furthermore, in large scale batch operations, (where stacks of DU rods are processed in quench baskets) the rods do not experience uniform quenching conditions. This gives rise to residual thermal stresses sufficiently large to cause bowing in the rods. More additional mechanical processing steps (i.e. straightening) are thus necessary to realign the deformed rods. The present technique of eliminating the bowing in the rods involve a three-point bend operation. This realignment operation introduces additional stresses in the rods, and is unsatisfactory for that reason. Any additional residual stress introduced into the rods is likely to increase susceptibility to stress corrosion cracking. Such stresses adversely affect the material by lowering its toughness and ductility. Furthermore, subsequent aging at 350.degree. C. will not substantially relieve these residual stresses.